Our preliminary data demonstrates that chronic administration of estradiol has dramatic inhibitory effects on basal and stimulated exocrine pancreatic secretion. Little is known however, about the molecular mechanisms that mediate the effects of estrogens on the exocrine pancreas. Therefore, from the standpoint of integrative physiology and pathophysiology it is imperative to identify and characterize the components of these mechanisms. It is our hypothesis that the adaptive response of the exocrine pancreas to estradiol administration is mediated via alterations in the transcription, expression and activity of components of exocrine pancreatic stimulus-secretion coupling mechanisms. This proposal contains studies designed to examine the molecular mechanisms mediating the effects of estradiol on CCK-stimulated exocrine pancreatic secretion. Studies are planned, utilizing chronic treatment of Sprague-Dawley rats with estradiol, isolating their pancreatic acini and examining the effect of these treatments on pancreatic stimulus-secretion coupling pathways, mRNA levels and protein expression. In our preliminary data we show that chronic estradiol administration dose-dependently regulates acinar cell amylase content and CCK-stimulated amylase release from rat pancreatic acini. Because previous studies have examined stimulated release of amylase isolation, this proposal includes studies to determine whether the CCK-stimulated release of other pancreatic enzymes is also regulated by estradiol. Moreover, we will examine the mechanisms involved in the regulation of acinar enzyme content and release at the molecular level. Additionally, the influence of estradiol on mRNA encoding CCKA receptors will be examined by preparing probes from cDNAs encoding this receptor and using these probes in ribonuclease protection assays. Generation of antisera against synthetic peptides or cloned receptor proteins expressed in E. Coli will permit immunoblotting to determine effects on receptor protein expression. These studies will yield information that will lead us to a more in depth examination of the mechanisms utilized by estradiol in the regulation of exocrine pancreatic secretion. For instance should we find differences in receptor mRNA levels between estradiol-treated and untreated groups we would pursue the effects of estradiol on receptor gene expression and mRNA stability. Such studies would lead to identification of cis- and trans- acting regulatory elements affecting receptor gene expression. The proposed studies will allow the elucidation of mechanisms through which estrogens regulate exocrine pancreatic function in rats and enhance the overall understanding of integrative regulation of the exocrine pancreas.